Aru and ARU may refer to:
- Aru
- Aru Islands, a group of islands in the Moluccas
- Sultanate of Deli (also known as Aru), an early Islamic polity in northeast Sumatra
- Aru, Democratic Republic of Congo, a town in Ituri province
- Aru, Harju County, village in Kuusalu Parish, Harju County, Estonia
- Aru, Saare County, village in Leisi Parish, Saare County, Estonia
- Aru, Damavand, village in Damavand County, Tehran Province, Iran
- Aru, Firuzkuh, village in Firuzkuh County, Tehran Province, Iran
- Aru, Jammu and Kashmir, village in India
- ARU
- Alpha Rho Upsilon, a defunct fraternity in the United States
- American Railway Union, an industrial union in the United States
- Anglia Ruskin University, a university in England
- Aquarium Rescue Unit, an American jazz-rock band
- Armed Response Unit, a special unit in the British police force
- Army Rugby Union, organisational body for rugby union in the British Army
- The National Rail code for Arundel railway station, a railway station in England
- Australian Rugby Union, governing body for rugby union in Australia
- Interactive voice response (also Audio or Automated response unit), a telecommunications device
- Autonomous Recording Unit, an audio recording device